Solar cell and method for manufacturing the same

ABSTRACT

A solar cell and a method for manufacturing the same are disclosed. The solar cell includes a semiconductor substrate containing impurities of a first conductive type, a tunnel layer positioned on the semiconductor substrate, an emitter region positioned on the tunnel layer and containing impurities of a second conductive type opposite the first conductive type, a dopant layer positioned on the emitter region and formed of a dielectric material containing impurities of the second conductive type, a first electrode connected to the semiconductor substrate, and a second electrode configured to pass through the dopant layer and connected to the emitter region.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2014-0152372 filed in the Korean IntellectualProperty Office on Nov. 4, 2014, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a solar cell and a method formanufacturing the same.

2. Description of the Related Art

Recently, as existing energy sources such as petroleum and coal areexpected to be depleted, interests in alternative energy sources forreplacing the existing energy sources are increasing. Among thealternative energy sources, solar cells for generating electric energyfrom solar energy have been particularly spotlighted.

A solar cell generally includes semiconductor parts, which respectivelyhave different conductive types, for example, a p-type and an n-type andthus form a p-n junction, and electrodes respectively connected to thesemiconductor parts of the different conductive types.

When light is incident on the solar cell, a plurality of electron-holepairs are produced in the semiconductor parts and are separated intoelectrons and holes by the incident light. The electrons move to then-type semiconductor part, and the holes move to the p-typesemiconductor part. Then, the electrons and the holes are collected bythe different electrodes respectively connected to the n-typesemiconductor part and the p-type semiconductor part. The electrodes areconnected to each other using electric wires to thereby obtain electricpower.

SUMMARY OF THE INVENTION

In one aspect, there is a solar cell including a semiconductor substratecontaining impurities of a first conductive type, a tunnel layerpositioned on the semiconductor substrate, an emitter region positionedon the tunnel layer and containing impurities of a second conductivetype opposite the first conductive type, a dopant layer positioned onthe emitter region and formed of a dielectric material containingimpurities of the second conductive type, a first electrode connected tothe semiconductor substrate, and a second electrode configured to passthrough the dopant layer, and connected to the emitter region.

A doping concentration of the second conductive type impuritiescontained in the emitter region in a first portion of the emitter regioncontacting the second electrode may be higher than the dopingconcentration in a second portion of the emitter region contacting thetunnel layer.

A doping concentration of the second conductive type impuritiescontained in the emitter region may increase in the emitter region ingoing away from the tunnel layer.

More specifically, a first doping concentration of the second conductivetype impurities in the first portion of the emitter region contactingthe second electrode may be higher than a second doping concentration ofthe second conductive type impurities in the second portion of theemitter region contacting the tunnel layer.

For example, the first doping concentration may be 5*10¹⁹/cm³ to5*10²¹/cm³, and the second doping concentration may be 5*10¹⁸/cm³ to5*10²⁰/cm³.

The doping concentration of the emitter region may successively decreaselinearly or nonlinearly in the emitter region in going from the firstportion to the second portion.

The emitter region may be formed of a polycrystalline silicon material.A crystallinity of the emitter region may increase in the emitter regionin going away from the tunnel layer.

A thickness of the emitter region may be 50 nm to 150 nm, and athickness of the dopant layer may be 25 nm to 150 nm.

The solar cell may further include a hydrogen injection layer positionedon a back surface of the dopant layer and formed of a dielectricmaterial containing hydrogen at a higher concentration than that of thedopant layer.

The solar cell may further include a front surface field regionpositioned on a front surface of the semiconductor substrate andcontaining impurities of the first conductive type at a higherconcentration than that of the semiconductor substrate. The tunnellayer, the emitter region, and the dopant layer may be positioned on aback surface of the semiconductor substrate.

In another aspect, there is a method for manufacturing a solar cell, themethod including a layer forming operation of sequentially forming atunnel layer, an intrinsic amorphous silicon layer, and a dopant layeron a back surface of a semiconductor substrate formed of a crystallinesilicon material containing impurities of a first conductive type, thedopant layer being formed of a dielectric material containing impuritiesof a second conductive type opposite the first conductive type; athermal processing operation of, after the layer forming operation,forming a front surface field region on a front surface of thesemiconductor substrate through one successive thermal process, in whicha temperature in a furnace is maintained or raised, recrystallizing theintrinsic amorphous silicon layer into an intrinsic polycrystallinesilicon layer, and diffusing and activating the impurities of the secondconductive type of the dopant layer into the recrystallized intrinsicpolycrystalline silicon layer to form an emitter region; and anelectrode forming operation of, after the thermal processing operation,forming a first electrode connected to the front surface of thesemiconductor substrate and forming a second electrode connected to theemitter region.

The layer forming operation may further include a process for forming acapping layer formed of a dielectric material not containing impuritiesof the second conductive type on a back surface of the dopant layer.

The method may further include, between the thermal processing operationand the electrode forming operation, an operation of removing a cappinglayer formed on the back surface of the semiconductor substrate and anoxide layer formed on a front surface of the front surface field regionin the thermal processing operation; and an operation of forming ahydrogen injection layer formed of a dielectric layer containinghydrogen on the back surface of the dopant layer, on which the cappinglayer is removed.

The forming of the emitter region may include a dehydrogenation processfor removing hydrogen contained in the intrinsic amorphous siliconlayer; a recrystallization process for recrystallizing the intrinsicamorphous silicon layer into the intrinsic polycrystalline siliconlayer; and an emitter region activating process for diffusing andactivating the impurities of the second conductive type contained in thedopant layer into the recrystallized intrinsic polycrystalline siliconlayer.

The forming of the front surface field region may include a frontsurface field region activating process for diffusing and activatingimpurities of the first conductive type into the front surface of thesemiconductor substrate. The front surface field region activatingprocess may be performed along with the emitter region activatingprocess.

The thermal processing operation may include a first thermal process formaintaining the temperature of the furnace at a first temperature, asecond thermal process for changing the temperature of the furnace fromthe first temperature to a second temperature higher than the firsttemperature, a third thermal process for maintaining the temperature ofthe furnace at the second temperature, a fourth thermal process forchanging the temperature of the furnace from the second temperature to athird temperature higher than the second temperature, and a fifththermal process for maintaining the temperature of the furnace at thethird temperature.

The first to fifth thermal processes may be successively performed inthe same furnace.

A second thermal process time of the second thermal process may belonger than a first thermal process time of the first thermal processand a third thermal process time of the third thermal process. The thirdthermal process time may be equal to or longer than the first thermalprocess time.

For example, the first thermal process may maintain the temperature ofthe furnace at the first temperature of 350° C. to 450° C. for 5 minutesto 15 minutes. The third thermal process may maintain the temperature ofthe furnace at the second temperature of 500° C. to 600° C. for 10minutes to 20 minutes.

The second thermal process may increase the temperature of the furnacefrom the first temperature to the second temperature for 15 minutes to25 minutes.

The fifth thermal process may maintain the temperature of the furnace atthe third temperature of 800° C. to 1000° C. for 15 minutes to 30minutes. The fourth thermal process may increase the temperature of thefurnace from the second temperature to the third temperature for 5minutes to 15 minutes.

The dehydrogenation process may be performed through the first to thirdthermal processes. The recrystallization process may be performedthrough the fourth thermal process.

The emitter region activating process and the front surface field regionactivating process may be performed through the fifth thermal process.

The solar cell and the method for manufacturing the same according tothe present disclosure are configured so that the doping concentrationof impurities of the second conductive type contained in the emitterregion increases as the emitter region is far away from the tunnellayer. Hence, a recombination of carriers in the emitter region can bereduced, and contact characteristic between the emitter region and thesecond electrode can be further improved.

Furthermore, the method for manufacturing the solar cell according tothe present disclosure simultaneously forms the front surface fieldregion and the emitter region through one successive thermal process, ofwhich a temperature is maintained or raised, and thus can further reducemanufacturing time.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIGS. 1 and 2 illustrate a solar cell according to an example embodimentof the invention;

FIG. 3 illustrates a doping concentration of an emitter region of thesolar cell shown in FIG. 1;

FIG. 4 illustrates a doping concentration of an emitter region accordingto a comparative example different from an example embodiment of theinvention;

FIG. 5 is a flow chart illustrating a method for manufacturing a solarcell according to an example embodiment of the invention;

FIGS. 6A to 6E depicts reference figures of each stage illustrated inthe flow chart of FIG. 5; and

FIG. 7 illustrates changes in a temperature over time in a thermalprocessing operation of a method for manufacturing a solar cellaccording to an example embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the invention,examples of which are illustrated in the accompanying drawings. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts. It will be noted that adetailed description of known arts will be omitted if it is determinedthat the detailed description of the known arts can obscure theembodiments of the invention.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. It will be understood that when an elementsuch as a layer, film, region, or substrate is referred to as being “on”another element, it can be directly on the other element or interveningelements may also be present. In contrast, when an element is referredto as being “directly on” another element, there are no interveningelements present. Further, it will be understood that when an elementsuch as a layer, film, region, or substrate is referred to as being“entirely” on other element, it may be on the entire surface of theother element and may not be on a portion of an edge of the otherelement.

In the following description, a “front surface” may be one surface of asemiconductor substrate, on which light is directly incident, and a“back surface” may be a surface opposite the one surface of thesemiconductor substrate, on which light is not directly incident orreflective light may be incident.

Exemplary embodiments of the invention are described with reference toFIGS. 1 to 7.

FIGS. 1 and 2 illustrate a solar cell according to an example embodimentof the invention. More specifically, FIG. 1 is a partial perspectiveview of the solar cell according to the embodiment of the invention, andFIG. 2 is a cross-sectional view taken along line II-II of FIG. 1.

As shown in FIGS. 1 and 2, a solar cell according to the embodiment ofthe invention may include a semiconductor substrate 110, a tunnel layer160, an emitter region 120, a dopant layer 180, a hydrogen injectionlayer 190, a front surface field region 170, a passivation layer 131, ananti-reflection layer 133, a first electrode 140, and a second electrode150.

In the embodiment disclosed herein, the anti-reflection layer 133, thepassivation layer 131, and the hydrogen injection layer 190 may beomitted, if desired or necessary. However, when the solar cell includesthe anti-reflection layer 133, the passivation layer 131, and thehydrogen injection layer 190 as shown in FIGS. 1 and 2, efficiency ofthe solar cell may be further improved. Thus, the embodiment of theinvention is described using the solar cell including theanti-reflection layer 133, the passivation layer 131, and the hydrogeninjection layer 190 as an example.

The semiconductor substrate 110 may be formed of crystalline siliconmaterial containing impurities of a first conductive type. For example,the semiconductor substrate 110 may be formed using a single crystalwafer or a polycrystalline wafer.

The impurities of the first conductive type may be p-type impurities,for example, impurities of a group III element, such as boron (B),gallium (Ga), and indium (In). Alternatively, the impurities of thefirst conductive type may be n-type impurities, for example, impuritiesof a group V element, such as phosphorus (P), arsenic (As), and antimony(Sb). The impurities of the first conductive type may be doped on thesemiconductor substrate 110. In the following description, theembodiment of the invention is described using an example where thefirst conductive type is the n-type.

A front surface of the semiconductor substrate 110 may be textured toform a textured surface corresponding to an uneven surface having aplurality of uneven portions or having uneven characteristics, so as tominimize a reflectance of incident light.

When light is incident on the semiconductor substrate 110, electron-holepairs are produced in the semiconductor substrate 110.

The tunnel layer 160 may be entirely formed on one surface, for example,a back surface of the semiconductor substrate 110. The tunnel layer 160may pass through carriers produced in the semiconductor substrate 110and may perform a passivation function with respect to the back surfaceof the semiconductor substrate 110.

The tunnel layer 160 may be formed of a dielectric material. Morespecifically, the tunnel layer 160 may be formed of silicon carbide(SiCx) or silicon oxide (SiOx) having strong durability at a hightemperature equal to or higher than 600° C. In addition, the tunnellayer 160 may be formed of silicon nitride (SiNx), hydrogenated SiNx,aluminum oxide (AlOx), silicon oxynitride (SiON), or hydrogenated SiON.

Unlike this, if the tunnel layer 160 is formed of a material includingamorphous silicon (a-Si), the tunnel layer 160 cannot obtain a desiredtunneling effect because amorphous silicon is weak or susceptible to thehigh temperature equal to or higher than 600° C.

A thickness of the tunnel layer 160 may be 0.5 nm to 2.5 nm.

The emitter region 120 may directly contact the tunnel layer 160 and maybe positioned on the entire back surface of the tunnel layer 160.

The emitter region 120 may be formed by doping impurities of a secondconductive type opposite the first conductive type on a polycrystallinesilicon material layer. For example, the emitter region 120 may beformed of polycrystalline silicon material containing impurities of thesecond conductive type.

In other words, the emitter region 120 may contain impurities of thesecond conductive type, for example, p-type impurities. For example, theemitter region 120 may contain impurities of a group III element, suchas boron (B), gallium (Ga), and indium (In).

The emitter region 120 may form a p-n junction along with thesemiconductor substrate 110 with the tunnel layer 160 interposedtherebetween. In another example, if the first conductive type of thesemiconductor substrate 110 is the p-type, the emitter region 120 may beof the n-type.

The polycrystalline silicon material layer of the emitter region 120 maybe obtained by re-crystallizing an amorphous silicon material layer.

Accordingly, the polycrystalline silicon material of the emitter region120 may have almost the same crystallinity throughout the emitter region120. Alternatively, the crystallinity of the polycrystalline siliconmaterial of the emitter region 120 may increase as the emitter region120 is far away from the tunnel layer 160.

Namely, the crystallinity in a first portion PT1 of the emitter region120 connected to the second electrode 150 may be relatively high, andthe crystallinity in a second portion PT2 of the emitter region 120closer to the tunnel layer 160 than the first portion PT1 may berelatively low.

Accordingly, a contact resistance between the emitter region 120 and thesecond electrode 150 may be further improved by the relatively highercrystallinity in the first portion PT1 of the emitter region 120connected to the second electrode 150.

When the emitter region 120 including the recrystallized polycrystallinesilicon material is formed at the back surface of the tunnel layer 160in a state where the tunnel layer 160 is positioned on the back surfaceof the semiconductor substrate 110, an open-circuit voltage of the solarcell may be further improved, and a damage of the semiconductorsubstrate 110 resulting from heat generated in a manufacturing processof the solar cell may be minimized. Hence, the solar cell with highefficiency may be implemented.

A thickness T120 of the emitter region 120 may be 50 nm to 150 nm.

When the thickness T120 of the emitter region 120 is equal to or greaterthan 50 nm, a function of the emitter region 120 forming the p-njunction along with the semiconductor substrate 110 may be secured. Whenthe thickness T120 of the emitter region 120 is equal to or less than 50nm, a process time may be minimized through the optimization of thethickness T120 of the emitter region 120 while the function of theemitter region 120 is maintained. Other thicknesses may be used for theemitter region 120.

A doping concentration of the impurities of the second conductive typecontained in the emitter region 120 may increase as the emitter region120 is far away from the tunnel layer 160. Hence, carriers arerecombined in the second portion PT2 of the emitter region 120relatively closer to the semiconductor substrate 110 due to theimpurities of the second conductive type, and a loss amount of carriersmay be further reduced. As a result, passivation characteristic may befurther improved. Further, the contact resistance between the emitterregion 120 and the second electrode 150 may be further improved in thefirst portion PT1 of the emitter region 120 connected to the secondelectrode 150 due to a relatively higher doping concentration.

Changes in the doping concentration of the emitter region 120 will beseparately described in detail with reference to FIG. 3.

The dopant layer 180 is positioned on the emitter region 120 and maycontain impurities of the second conductive type. A dielectric materialof the dopant layer 180 may include at least one of silicon nitride(SiNx), silicon oxide (SiOx), silicon oxynitride (SiOxNy), siliconcarbide (SiCx), or aluminum oxide (AlOx). Thus, the dopant layer 180 maycontain SiOx:B containing boron (B) as an example of the impurities ofthe second conductive type.

The dopant layer 180 functions to diffuse the impurities of the secondconductive type contained in the dielectric material into an intrinsicpolycrystalline silicon layer in a process for forming the emitterregion 120. After the emitter region 120 is formed, the dopant layer 180receives hydrogen from the hydrogen injection layer 190 formed on a backsurface of the dopant layer 180 and may perform a passivation functionwith respect to the back surface of the emitter region 120.

A thickness of the dopant layer 180 may be 25 nm to 150 nm. When thethickness of the dopant layer 180 is equal to or greater than 25 nm, aminimum amount of impurities of the second conductive type to bediffused into the emitter region 120 may be secured. When the thicknessof the dopant layer 180 is equal to or less than 150 nm, the processtime may be minimized through the optimization of the thickness of thedopant layer 180 while an amount of impurities of the second conductivetype is properly secured. Further, an effusion speed of hydrogencontained in the intrinsic polycrystalline silicon layer for forming theemitter region 120 may be properly controlled in a dehydrogenationprocess. Other thicknesses may be used for the dopant layer 180.

The hydrogen injection layer 190 positioned on the back surface of thedopant layer 180 may be formed of a dielectric material containinghydrogen at a higher concentration than the dielectric material of thedopant layer 180.

After the formation of the emitter region 120 is completed, the hydrogeninjection layer 190 may be formed on the back surface of the dopantlayer 180. In an electrode forming operation involving a thermalprocessing, hydrogen of the high concentration contained in the hydrogeninjection layer 190 may be diffused into the dopant layer 180, so thatthe dopant layer 180 has the passivation function.

The hydrogen injection layer 190 may have a refractive index differentfrom the dopant layer 180, so that light, which is incident on the solarcell and is transmitted by the semiconductor substrate 110, is againincident on the semiconductor substrate 110.

The dielectric material of the hydrogen injection layer 190 may includeat least one of SiNx, SiOx, SiOxNy, SiCx, or AlOx.

The front surface field region 170 is positioned at the front surface ofthe semiconductor substrate 110 and may be more heavily doped than thesemiconductor substrate 110 with impurities of the first conductivetype.

The front surface field region 170 may be formed by diffusing impuritiesof the first conductive type into the front surface of the semiconductorsubstrate 110. Hence, the front surface field region 170 may be formedof the same crystalline silicon material as the semiconductor substrate110.

For example, when the semiconductor substrate 110 is formed of a singlecrystal silicon material, the front surface field region 170 may beformed of the single crystal silicon material. Alternatively, when thesemiconductor substrate 110 is formed of a polycrystalline siliconmaterial, the front surface field region 170 may be formed of thepolycrystalline silicon material.

The passivation layer 131 is positioned directly on a front surface ofthe front surface field region 170 and may perform a passivationfunction with respect to the front surface of the front surface fieldregion 170. The passivation layer 131 may be formed of a dielectricmaterial containing hydrogen. For example, the passivation layer 131 maybe formed of at least one of SiNx, SiOx, SiOxNy, or AlOx.

The anti-reflection layer 133 is positioned on a front surface of thepassivation layer 131. The anti-reflection layer 133 may improvetransmission of light incident on the solar cell and reduce areflectance of the light. Hence, the anti-reflection layer 133 may makea large amount of light be incident on the semiconductor substrate 110.

The anti-reflection layer 133 may be formed of a dielectric materialcontaining hydrogen. For example, the anti-reflection layer 133 may beformed of at least one of SiNx, SiOx, SiOxNy, or AlOx.

The first electrode 140 is positioned on the front surface of thesemiconductor substrate 110. The first electrode 140 may pass throughthe anti-reflection layer 133 and the passivation layer 131 and may beconnected to the front surface field region 170.

The first electrode 140 may include a plurality of first fingerelectrodes 141 and a plurality of first bus bars 142 connected to theplurality of first finger electrodes 141.

The first finger electrodes 141 may be electrically and physicallyconnected to the front surface field region 170. The first fingerelectrodes 141 may be separated from one another and may extend inparallel with one another in a first direction x. The first fingerelectrodes 141 may collect carriers (for example, electrons) moving tothe front surface field region 170.

The first bus bars 142 may be electrically and physically connected tothe emitter region 120 and may extend in parallel with one another in asecond direction y crossing the first finger electrodes 141.

The first bus bar 142 may be positioned on the same layer as the firstfinger electrode 141 and may be electrically and physically connected tothe first finger electrode 141 at a location crossing the first fingerelectrode 141.

As shown in FIG. 1, the plurality of first finger electrodes 141 mayhave a stripe shape extending in the first direction x, and theplurality of first bus bars 142 may have a stripe shape extending in thesecond direction y. Hence, the first electrode 140 may have a latticeshape at the front surface of the semiconductor substrate 110.

The plurality of first bus bars 142 may collect not only carrier movingfrom the front surface field region 170 contacting the first bus bars142 but also carriers collected by the plurality of first fingerelectrodes 141.

The first bus bars 142 have to collect carriers collected by the firstfinger electrodes 141 crossing the first bus bars 142 and have to movethe collected carriers in a desired direction. Therefore, a width ofeach first bus bar 142 may be greater than a width of each first fingerelectrode 141.

The plurality of first bus bars 142 may be connected to an externaldevice and may output the collected carriers (for example, electrons) tothe external device.

The plurality of first finger electrodes 141 and the plurality of firstbus bars 142 of the first electrode 140 may be formed of at least oneconductive material, for example, silver (Ag).

The second electrode 150 is positioned on the back surface of thesemiconductor substrate 110. The second electrode 150 may pass throughthe dopant layer 180 and the hydrogen injection layer 190 and may beconnected to the emitter region 120.

As shown in FIGS. 1 and 2, the second electrode 150 may include aplurality of second finger electrodes 151 and a plurality of second busbars 152 connected to the plurality of second finger electrodes 151 inthe same manner as the first electrode 140. The second electrode 150 mayhave the same pattern as the first electrode 140. Other patterns may beused for the second electrode 150.

The second electrode 150 may collect carriers (for example, holes)moving to the emitter region 120.

FIGS. 1 and 2 show that the emitter region 120 is positioned on the backsurface of the semiconductor substrate 110 and the front surface fieldregion 170 is positioned on the front surface of the semiconductorsubstrate 110, as an example. In another example, the emitter region 120may be positioned on the front surface of the semiconductor substrate110, and the front surface field region 170 may be positioned on theback surface of the semiconductor substrate 110. The another example maybe equally applied to the embodiment of the invention.

In the solar cell according to the embodiment of the invention, thedoping concentration of the impurities of the second conductive typecontained in the emitter region 120 may entirely increase as the emitterregion 120 is far away from the tunnel layer 160.

This is described in detail below with reference to FIG. 3.

FIG. 3 illustrates a doping concentration of the emitter region of thesolar cell shown in FIG. 1. FIG. 4 illustrates a doping concentration ofan emitter region according to a comparative example different from theembodiment of the invention.

More specifically, FIGS. 3 and 4 show an example of a dopingconcentration depending on the cross-section of the emitter region 120and the semiconductor substrate 110. In FIGS. 3 and 4, x-axis denotes adepth toward the semiconductor substrate 110 from the back surface ofthe emitter region 120 contacting the second electrode 150, and y-axisdenotes a doping concentration.

FIG. 3 shows an example of the doping concentration when the thicknessT120 of the emitter region 120 is about 150 nm, for example. However,the thickness T120 of the emitter region 120 may be variously determinedbetween 50 nm and 150 nm. Further, the doping concentration shown inFIG. 3 is merely an example and thus may be variously changed.

As shown in FIG. 3, the doping concentration of the emitter region 120according to the embodiment of the invention may be higher than a dopingconcentration of the semiconductor substrate 110.

A first doping concentration C1 of second conductive type impurities inthe first portion PT1 (at a depth of 0 nm) of the emitter region 120contacting the second electrode 150 may be higher than a second dopingconcentration C2 of second conductive type impurities in the secondportion PT2 (at a depth of 150 nm) of the emitter region 120 contactingthe tunnel layer 160.

The first portion PT1 indicates a contact portion of the emitter region120 and the second electrode 150 or a contact portion of the emitterregion 120 and the dopant layer 180. The second portion PT2 indicates acontact portion of the emitter region 120 and the tunnel layer 160.

In FIG. 3, for example, the first doping concentration C1 is1.2*10²¹/cm³, and the second doping concentration C2 is 1.3*10²⁰/cm³.However, the first doping concentration C1 may be determined between5*10¹⁹/cm³ and 5*10²¹/cm³, and the second doping concentration C2 may bedetermined between 5*10¹⁸/cm³ and 5*10²⁰/cm³ and may be lower than thefirst doping concentration C1.

The doping concentration of the emitter region 120 may increase as theemitter region 120 is far away from the tunnel layer 160. Morespecifically, as the emitter region 120 goes from the first portion PT1to the second portion PT2, the doping concentration of the emitterregion 120 may successively decrease linearly or nonlinearly.

In FIG. 3, for example, as the emitter region 120 goes from the firstportion PT1 to the second portion PT2, the doping concentration of theemitter region 120 successively and nonlinearly decreases from the firstdoping concentration C1 to the second doping concentration C2. However,the doping concentration of the emitter region 120 may successively andlinearly decrease.

The characteristic of the emitter region 120, in which the dopingconcentration of the emitter region 120 increases as the emitter region120 is far away from the tunnel layer 160, may be generated in a thermalprocessing operation of diffusing the second conductive type impuritiesof the dopant layer 180 into a polycrystalline silicon layerrecrystallized through a process for recrystallizing an intrinsicamorphous silicon layer into a polycrystalline silicon layer byperforming one successive thermal process, of which the temperaturechanges, in a state where an intrinsic amorphous silicon layer isfirstly formed. Hence, the emitter region 120 is formed.

In the second portion PT2 of the emitter region 120 relatively close tothe semiconductor substrate 110, carriers may be recombined byimpurities, and a loss amount of carriers may be further reduced due tothe above characteristic of the emitter region 120, in which the dopingconcentration of the emitter region 120 increases as the emitter region120 is far away from the tunnel layer 160. Hence, the passivationcharacteristic may be further improved. In the first portion PT1 of theemitter region 120 connected to the second electrode 150, the contactresistance between the emitter region 120 and the second electrode 150may be further improved due to the relatively higher dopingconcentration of the emitter region 120.

Unlike the embodiment of the invention shown in FIG. 3, in thecomparative example of FIG. 4, when impurities of the second conductivetype are diffused in a state an intrinsic polycrystalline silicon layeris deposited and formed, a doping concentration of the emitter region120 does not entirely increase as the emitter region 120 goes from thefirst portion PT1 to the second portion PT2. In this instance, thedoping concentration of the emitter region 120 slightly changes, but isentirely uniform around 1.5*10²⁰/cm³.

It may be difficult for the comparative example of FIG. 4 to secure thesame effect as the embodiment of the invention. Namely, when thecomparative example increases the doping concentration so as to improvethe contact characteristic between the emitter region 120 and the secondelectrode 150, an amount of carriers recombined in the emitter region120 may increase because the doping concentration of the emitter region120 itself entirely increases. Hence, the characteristic of the emitterregion 120 may be reduced. When the comparative example decreases thedoping concentration so as to improve the characteristic of the emitterregion 120, the contact resistance between the emitter region 120 andthe second electrode 150 may increase. Hence, characteristic of a shortcircuit current of the solar cell may be reduced.

So far, the embodiment of the invention described an example of thestructure of the solar cell. Hereinafter, the embodiment of theinvention will describe an example of a method for manufacturing thesolar cell.

FIG. 5 is a flow chart illustrating a method for manufacturing the solarcell according to the embodiment of the invention. FIGS. 6A to 6Edepicts reference figures of each stage illustrated in the flow chart ofFIG. 5.

As shown in FIG. 5, the method for manufacturing the solar cellaccording to the embodiment of the invention may include a layer formingoperation S1, a thermal processing operation S2, an operation S3 ofremoving a capping layer and an oxide layer, a hydrogen injection layerforming operation S4, and an electrode forming operation S5.

The operation S3 for removing a capping layer and an oxide layer and thehydrogen injection layer formation operation S4 may be omitted, ifnecessary or desired. However, when the method for manufacturing thesolar cell includes the operations S3 and S4, the efficiency of thesolar cell thus manufactured may be further improved. Thus, theembodiment of the invention is described using the method formanufacturing the solar cell including the operations S3 and S4 as anexample.

As shown in FIG. 5, in the layer forming operation S1, a tunnel layerforming process P1, an intrinsic amorphous silicon layer forming processP2, a dopant layer forming process P3, and a capping layer formingprocess P4 may be performed.

More specifically, referring to FIG. 6A, in the tunnel layer formingprocess P1, SiCx or SiOx may be deposited on the back surface of thesemiconductor substrate 110 formed of crystalline silicon materialcontaining impurities of the first conductive type to form the tunnellayer 160 on the entire back surface of the semiconductor substrate 110.

Next, in the intrinsic amorphous silicon layer forming process P2, anintrinsic amorphous silicon layer 120A may be formed on the entire backsurface of the tunnel layer 160 through the deposition. In thisinstance, a thickness of the intrinsic amorphous silicon layer 120A maybe determined between 50 nm and 150 nm.

Next, in the dopant layer forming process P3, the dopant layer 180formed of a dielectric material containing impurities of the secondconductive type, for example, boron (B) may be formed on an entire backsurface of the intrinsic amorphous silicon layer 120A. In this instance,a thickness of the dopant layer 180 may be determined between 25 nm and150 nm.

Next, a capping layer CAP formed of a dielectric material not containingimpurities of the second conductive type may be formed on the entireback surface of the dopant layer 180. The dielectric material formingthe capping layer CAP may be at least one of SiOx, SiNx, SiOxNy, or SiCxnot containing impurities of the second conductive type. For example, itmay be more advantageous in the manufacturing process that the cappinglayer CAP is formed of SiOx so as to easily perform the subsequentoperation S3 of removing the capping layer and the oxide layer.

In a front surface field region forming process P5 of the subsequentthermal processing operation S2, the capping layer CAP may preventimpurities of the first conductive type from being diffused into theintrinsic amorphous silicon layer 120A. When a dehydrogenation processP61 of the subsequent thermal processing operation S2 is performed, thecapping layer CAP may control an amount and a speed of hydrogen emittedfrom the intrinsic amorphous silicon layer 120A.

In this instance, a sum of a thickness of the capping layer CAP and thethickness of the dopant layer 180 may be determined between 50 nm and150 nm.

Thus, when the thickness of the dopant layer 180 is 150 nm, the cappinglayer forming process P4 may be omitted.

The tunnel layer forming process P1, the intrinsic amorphous siliconlayer forming process P2, the dopant layer forming process P3, and thecapping layer forming process P4 of the layer forming operation Si maybe performed in-situ.

Namely, the processes P1 to P4 of the layer forming operation S1 may besuccessively performed while moving in a vacuum state between chambers,in which each of the processes P1 to P4 is performed in a vacuum statewithout being exposed in an atmosphere between the processes P1 to P4.Hence, the process time may be further reduced.

It is preferable, but not required, that the layer forming operation S1may be performed using a plasma enhanced chemical vapor deposition(PECVD) method performed at a temperature equal to or lower than 300° C.Alternatively, an atmospheric pressure chemical vapor deposition (APCVD)method or a low pressure chemical vapor deposition (LPCVD) method may beused.

After the layer forming operation S1 is performed, the thermalprocessing operation S2 may be performed.

The thermal processing operation S2 may be performed in a furnacethrough one successive thermal process, so as to form the front surfacefield region 170 and the emitter region 120.

The one successive thermal process, of which a temperature is maintainedor raised, is to successively provide a thermal process, of which atemperature is maintained or raised without a fall in the temperatureduring a period of the thermal processing operation S2. When thetemperature falls, one cycle of one thermal processing operation S2 iscompleted. The thermal process for maintaining or raising thetemperature may be performed several times.

Accordingly, the thermal processing operation S2 according to theembodiment of the invention forms the front surface field region 170 andthe emitter region 120 through only the one successive thermal process,in which the temperature does not fall and is maintained or raised, inone furnace. Hence, manufacturing time may be further reduced.

The successive thermal process, of which the temperature is maintainedor raised, is described in detail later with reference to FIG. 7.

In the thermal processing operation S2, the front surface field regionforming process P5 for forming the front surface field region 170 on thefront surface of the semiconductor substrate 110 and an emitter regionforming process P6 for recrystallizing the intrinsic amorphous siliconlayer 120A into an intrinsic polycrystalline silicon layer 120C anddiffusing impurities of the second conductive type of the dopant layer180 into the recrystallized intrinsic polycrystalline silicon layer 120Cto form the emitter region 120 may be performed together.

The front surface field region forming process P5 may include animpurity injection process P51 and a front surface field regionactivating process P52.

In the impurity injection process P51, POCl₃ gas containing impuritiesof the first conductive type may be injected into the furnace. In thefront surface field region activating process P52, as shown in FIG. 6B,phosphorus (P) corresponding to impurities of the first conductive typein the POCl₃ gas may be diffused into the front surface of thesemiconductor substrate 110 and activated.

In this instance, phosphorus (P) of the POCl₃ gas may be prevented frombeing diffused into the intrinsic amorphous silicon layer 120A or theintrinsic polycrystalline silicon layer 120C by the capping layer CAPand the dopant layer 180 on the back surface of the semiconductorsubstrate 110.

The front surface field region activating process P52 may be performedthrough a thermal process of 800° C. to 1000° C.

An oxide layer SOL may be unnecessarily formed on the front surface ofthe front surface field region 170 in the front surface field regionactivating process P52. The oxide layer SOL may be removed together whenthe capping layer CAP is removed later.

The embodiment of the invention described that the front surface fieldregion forming process P5 of the thermal processing operation S2 in theflow chart shown in FIG. 5 includes the impurity injection process P51for injecting the POCl₃ gas containing impurities of the firstconductive type into the furnace, as an example. However, a dopantsource may be formed.

Namely, the front surface field region forming process P5 may apply adopant paste containing impurities of the first conductive type or formthe dopant paste on the front surface of the semiconductor substrate 110in a SOD (spin on dopant) method instead of performing the impurityinjection process P51 before the thermal processing operation S2 afterthe layer forming operation S1, and then may diffuse and activate theimpurities of the first conductive type into the front surface of thesemiconductor substrate 110 in the front surface field region activatingprocess P52 of the thermal processing operation S2.

Alternatively, the front surface field region forming process P5 maypreviously implant the dopant paste formed on the front surface of thesemiconductor substrate 110 onto the front surface of the semiconductorsubstrate 110 using a laser irradiation device before the thermalprocessing operation S2 after the layer forming operation S1, and thenmay perform the front surface field region activating process P52.

Next, the emitter region forming process P6 may include thedehydrogenation process P61, a recrystallization process P62, and anemitter region activating process P63.

The dehydrogenation process P61 is a thermal process for removinghydrogen contained in the intrinsic amorphous silicon layer 120A. Inother words, the dehydrogenation process P61 diffuses hydrogen containedin the intrinsic amorphous silicon layer 120A by increasing atemperature of the furnace and discharges hydrogen to the outside of theintrinsic amorphous silicon layer 120A through the dopant layer 180 andthe capping layer CAP.

When an amount or a speed of discharging of the hydrogen contained inthe intrinsic amorphous silicon layer 120A is excessively large, theintrinsic amorphous silicon layer 120A may be damaged. On the contrary,when the amount or the speed is small, the manufacturing time mayincrease. It is preferable, but not required, that the temperature inthe furnace is optimized so as to optimize the amount or the speed ofthe discharging of the hydrogen.

In this instance, the temperature in the furnace may be controlledbetween 350° C. and 600° C., for example.

The recrystallization process P62 is a process for recrystallizing theintrinsic amorphous silicon layer 120A into the intrinsicpolycrystalline silicon layer 120C. The recrystallization process P62may be performed by further increasing the temperature of the furnacewhen the dehydrogenation process P61 is almost completed. In therecrystallization process P62, the intrinsic amorphous silicon layer120A may start to be recrystallized between about 600° C. and 650° C.

Thus, the recrystallization process P62 may be performed at atemperature higher than the dehydrogenation process P61 and may besuccessively performed subsequent to the dehydrogenation process P61.The recrystallization process P62 may be performed by increasing thetemperature of the furnace by about 800° C. to 1000° C. from atemperature of the dehydrogenation process P61.

Through the recrystallization process P62, the crystallization of theintrinsic amorphous silicon layer 120A may start from the first portionPT1 contacting the dopant layer 180 and may be proceeded toward thesecond portion PT2 contacting the tunnel layer 160.

Thus, the crystallinity of the first portion PT1 may be higher than thecrystallinity of the second portion PT2. Further, as the emitter region120 goes from the first portion PT1 to the second portion PT2, thecrystallinity may gradually decrease. However, a reduction pattern ofthe crystallinity may be differently formed depending on time and thetemperature of the recrystallization process P62.

The emitter region activating process P63 is a process for diffusing andactivating impurities of the second conductive type contained in thedopant layer 180 shown in FIG. 6B into the recrystallized intrinsicpolycrystalline silicon layer 120C. The emitter region activatingprocess P63 may be performed by maintaining a maximum temperature of therecrystallization process P62.

Namely, the emitter region activating process P63 may be performed bymaintaining the temperature of the furnace at 800° C. to 1000° C.

The emitter region 120, in which impurities of the second conductivetype are doped on the intrinsic polycrystalline silicon layer 120Cthrough the emitter region activating process P63, may be completed.

During the emitter region activating process P63, the recrystallizationprocess P62 may be continuously performed. Because impurities of thesecond conductive type are diffused from the first portion PT1contacting the dopant layer 180 toward the second portion PT2 contactingthe tunnel layer 160, the first doping concentration C1 of the firstportion PT1 may be higher than the second doping concentration C2 of thesecond portion PT2. The doping concentration of the second conductivetype impurities may successively decrease as the emitter region 120 goesfrom the first portion PT1 to the second portion PT2.

As described above, the thermal processing operation S2 forsimultaneously forming the emitter region 120 and the front surfacefield region 170 may be performed through one successive thermalprocess, of which the temperature is maintained or raised. The onesuccessive thermal process, of which the temperature is maintained orraised, may greatly reduce the manufacturing time of the solar cell andmay improve the efficiency of the solar cell.

As shown in FIG. 5, after the thermal processing operation S2 iscompleted, the operation S3 of removing the capping layer and the oxidelayer and the hydrogen injection layer forming operation S4 may beperformed before the electrode forming operation S5. However, the aboveoperations are not necessary, and some of the above operations may beomitted.

In the operation S3 of removing the capping layer and the oxide layer,as shown in FIG. 6C, the capping layer CAP formed on the back surface ofthe semiconductor substrate 110 and the oxide layer SOL formed on thefront surface of the semiconductor substrate 110 in the thermalprocessing operation S2 may be removed using a general etchant removingthe oxide layer SOL.

In the embodiment disclosed herein, when the capping layer CAP is formedof, for example, SiOx, the operation S3 of removing the capping layerand the oxide layer may be more easily performed using the same etchantas the etchant removing the oxide layer SOL.

If the capping layer CAP is omitted in the layer forming operation S1,the operation of removing the capping layer CAP may be omitted.

Next, in the hydrogen injection layer forming operation S4, as shown inFIG. 6D, the hydrogen injection layer 190 which is formed of thedielectric material containing hydrogen at the high concentration, maybe formed on the back surface of the dopant layer 180, on which thecapping layer CAP is removed.

Because the hydrogen injection layer 190 contains hydrogen at the highconcentration, the passivation function of the dopant layer 180 and thetunnel layer 160 may be improved by supplying hydrogen to the dopantlayer 180 and the tunnel layer 160 in the subsequent electrode formingoperation S5.

In this instance, a hydrogen concentration of the hydrogen injectionlayer 190 may be equal to or higher than a hydrogen concentration of thedopant layer 180, to which hydrogen is supplied.

Further, as shown in FIG. 6D, a first electrode paste P140 for formingthe first electrode 140 and a second electrode paste P150 for formingthe second electrode 150 may be respectively patterned and applied onthe front surface and the back surface of the semiconductor substrate110 in a state where the passivation layer 131 and the anti-reflectionlayer 133 are formed on the front surface of the front surface fieldregion 170.

Next, as shown in FIGS. 5 and 6E, in the electrode forming operation S5,the first electrode paste P140 may pass through the passivation layer131 and the anti-reflection layer 133 through the thermal processing ofthe semiconductor substrate 110 to form the first electrode 140connected to the front surface of the semiconductor substrate 110.Further, the second electrode paste P150 may pass through the hydrogeninjection layer 190 and the dopant layer 180 through the thermalprocessing of the semiconductor substrate 110 to form the secondelectrode 150 connected to the emitter region 120.

The embodiment of the invention mainly described the method forming eachof the components of the solar cell so as to describe the method formanufacturing the solar cell. Hereinafter, one successive thermalprocess, of which the temperature of the thermal processing operation S2is maintained or raised, is described in detail.

FIG. 7 illustrates changes in a temperature over time in the thermalprocessing operation S2 of the method for manufacturing the solar cellaccording to the embodiment of the invention.

As shown in FIG. 7, a plurality of thermal processes may constitute onethermal processing operation S2. Namely, the plurality of thermalprocesses may form one cycle of the thermal processing operation S2.

The thermal processing operation S2 according to the embodiment of theinvention may include first to sixth thermal processes HT1 to HT6. Morespecifically, as shown in FIG. 7, the temperature of the thermalprocessing operation S2 does not fall and is maintained or raised in thefirst to fifth thermal processes HT1 to HT5 and falls in the sixththermal process HT6. Hence, one successive thermal operation S2, ofwhich the temperature changes, may be performed.

The first to sixth thermal processes HT1 to HT6 may be successivelyperformed in the same furnace.

More specifically, as shown in FIG. 7, a temperature of the furnace inthe first thermal process HT1 may be maintained at a first temperatureK1, and the temperature of the furnace in the second thermal process HT2may increase from the first temperature K1 to a second temperature K2higher than the first temperature K1. The temperature of the furnace inthe third thermal process HT3 may be maintained at the secondtemperature K2.

The dehydrogenation process P61 of the intrinsic semiconductor layer maybe performed in the first to third thermal processes HT1 to HT3.

In the embodiment disclosed herein, a second thermal process time T2 ofthe second thermal process HT2 may be longer than a first thermalprocess time T1 of the first thermal process HT1 and a third thermalprocess time T3 of the third thermal process HT3, and the third thermalprocess time T3 may be equal to or longer than the first thermal processtime T1.

More specifically, as shown in FIG. 7, the first thermal process HT1 maymaintain the temperature of the furnace at the first temperature K1 of350° C. to 450° C. for the first thermal process time T1 of 5 minutes to15 minutes. The third thermal process HT3 may maintain the temperatureof the furnace at the second temperature K2 of 500° C. to 600° C. forthe third thermal process time T3 of 10 minutes to 20 minutes, which isequal to or longer than the first thermal process time T1.

The second thermal process HT2 may increase the temperature of thefurnace from the first temperature K1 to the second temperature K2 forthe second thermal process time T2 of 15 minutes to 25 minutes, which islonger than the first thermal process time T1 and the third thermalprocess time T3.

The dehydrogenation process P61 of the intrinsic amorphous silicon layer120A may be optimally performed depending on the temperature and theprocess time of the first to third thermal processes HT1 to HT3.

The fourth thermal process HT4 may increase the temperature of thefurnace from the second temperature K2 to a third temperature K3 of 800°C. to 1000° C. higher than the second temperature K2 for a fourththermal process time T4 of 5 minutes to 15 minutes.

The intrinsic amorphous silicon layer 120A may be recrystallized throughthe fourth thermal process HT4 and may be changed into the intrinsicpolycrystalline silicon layer 120C.

The fifth thermal process HT5 may maintain the temperature of thefurnace at the third temperature K3 of 800° C. to 1000° C. for a fifththermal process time T5 of 15 minutes to 30 minutes, thereby diffusingand activating boron (B) corresponding to the second conductive typeimpurities of the dopant layer 180 into the recrystallized intrinsicpolycrystalline silicon layer 120C. Hence, the emitter region 120 may beformed. Further, phosphorus (P) corresponding to the first conductivetype impurities of POCl₃ gas injected into the furnace may be diffusedand activated into the front surface of the semiconductor substrate 110to form the front surface field region 170.

Namely, the recrystallization process P62 and the emitter regionactivating process P63 may be continuously performed together in thefifth thermal process HT5.

As described above, the method for manufacturing the solar cellaccording to the embodiment of the invention may simultaneously performthe emitter region activating process P63 and the front surface fieldregion activating process P52 through the fifth thermal process HT5.

Next, the sixth thermal process HT6 may reduce the temperature of thefurnace from the third temperature K3 to the first temperature K1 for asixth thermal process time T6. Hence, one thermal processing operationS2 may be completed. The sixth thermal process time T6 is notparticularly limited.

The method for manufacturing the solar cell according to the embodimentof the invention may diffuse and activate the first conductive typeimpurities and the second conductive type impurities through only onethermal process of the high temperature, unlike the generalmanufacturing method using at least two thermal processes performed at ahigh temperature equal to or higher than 800° C. Hence, a degradation ofthe semiconductor substrate 110 may be prevented, and an open-circuitvoltage and the efficiency of the solar cell may be further improved.

The embodiment of the invention may diffuse and activate the secondconductive type impurities at the same time as the recrystallization ofthe intrinsic amorphous silicon layer 120A into the intrinsicpolycrystalline silicon layer 120C. Thus, the doping concentration ofthe emitter region 120 may increase as the emitter region 120 is faraway from the tunnel layer 160.

Accordingly, the embodiment of the invention may further simplify themanufacturing process of the solar cell and may further improve theefficiency of the solar cell.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A solar cell comprising: a semiconductorsubstrate containing impurities of a first conductive type; a tunnellayer positioned on the semiconductor substrate; an emitter regionpositioned on the tunnel layer and containing impurities of a secondconductive type opposite the first conductive type; a dopant layerpositioned on the emitter region and formed of a dielectric materialcontaining impurities of the second conductive type; a first electrodeconnected to the semiconductor substrate; and a second electrodeconfigured to pass through the dopant layer, and connected to theemitter region.
 2. The solar cell of claim 1, wherein a dopingconcentration of the second conductive type impurities contained in theemitter region in a first portion of the emitter region contacting thesecond electrode is higher than the doping concentration in a secondportion of the emitter region contacting the tunnel layer.
 3. The solarcell of claim 1, wherein a doping concentration of the second conductivetype impurities contained in the emitter region increases in the emitterregion in going away from the tunnel layer.
 4. The solar cell of claim1, wherein a first doping concentration of the second conductive typeimpurities in a first portion of the emitter region contacting thesecond electrode is 5*10¹⁹/cm³ to 5*10²¹/cm³, and wherein a seconddoping concentration of the second conductive type impurities in asecond portion of the emitter region contacting the tunnel layer islower than the first doping concentration, and is 5*10¹⁸/cm³ to5*10²⁰/cm³.
 5. The solar cell of claim 2, wherein the dopingconcentration of the emitter region successively decreases linearly ornonlinearly in the emitter region in going from the first portion to thesecond portion.
 6. The solar cell of claim 1, wherein the emitter regionis formed of a polycrystalline silicon material, and wherein acrystallinity of the emitter region increases in the emitter region ingoing away from the tunnel layer.
 7. The solar cell of claim 1, whereina thickness of the emitter region is 50 nm to 150 nm, and wherein athickness of the dopant layer is 25 nm to 150 nm.
 8. The solar cell ofclaim 1, further comprising a hydrogen injection layer positioned on aback surface of the dopant layer and formed of a dielectric materialcontaining hydrogen at a higher concentration than that of the dopantlayer.
 9. The solar cell of claim 1, further comprising a front surfacefield region positioned on a front surface of the semiconductorsubstrate and containing impurities of the first conductive type at ahigher concentration than that of the semiconductor substrate, whereinthe tunnel layer, the emitter region, and the dopant layer arepositioned on a back surface of the semiconductor substrate.
 10. Amethod for manufacturing a solar cell, the method comprising: a layerforming operation of sequentially forming a tunnel layer, an intrinsicamorphous silicon layer, and a dopant layer on a back surface of asemiconductor substrate formed of a crystalline silicon materialcontaining impurities of a first conductive type, the dopant layer beingformed of a dielectric material containing impurities of a secondconductive type opposite the first conductive type; a thermal processingoperation of, after the layer forming operation, forming a front surfacefield region on a front surface of the semiconductor substrate throughone successive thermal process, in which a temperature in a furnace ismaintained or raised, recrystallizing the intrinsic amorphous siliconlayer into an intrinsic polycrystalline silicon layer, and diffusing andactivating the impurities of the second conductive type of the dopantlayer into the recrystallized intrinsic polycrystalline silicon layer toform an emitter region; and an electrode forming operation of, after thethermal processing operation, forming a first electrode connected to thefront surface of the semiconductor substrate and forming a secondelectrode connected to the emitter region.
 11. The method of claim 10,wherein the layer forming operation further includes a process forforming a capping layer formed of a dielectric material not containingimpurities of the second conductive type on a back surface of the dopantlayer.
 12. The method of claim 11, further comprising, between thethermal processing operation and the electrode forming operation: anoperation of removing a capping layer formed on the back surface of thesemiconductor substrate and an oxide layer formed on a front surface ofthe front surface field region in the thermal processing operation; andan operation of forming a hydrogen injection layer formed of adielectric layer containing hydrogen on the back surface of the dopantlayer, on which the capping layer is removed.
 13. The method of claim10, wherein the forming of the emitter region includes: adehydrogenation process for removing hydrogen contained in the intrinsicamorphous silicon layer; a recrystallization process for recrystallizingthe intrinsic amorphous silicon layer into the intrinsic polycrystallinesilicon layer; and an emitter region activating process for diffusingand activating the impurities of the second conductive type contained inthe dopant layer into the recrystallized intrinsic polycrystallinesilicon layer.
 14. The method of claim 13, wherein the forming of thefront surface field region includes a front surface field regionactivating process for diffusing and activating impurities of the firstconductive type into the front surface of the semiconductor substrate,and wherein the front surface field region activating process isperformed along with the emitter region activating process.
 15. Themethod of claim 14, wherein the thermal processing operation includes: afirst thermal process for maintaining the temperature of the furnace ata first temperature; a second thermal process for changing thetemperature of the furnace from the first temperature to a secondtemperature higher than the first temperature; a third thermal processfor maintaining the temperature of the furnace at the secondtemperature; a fourth thermal process for changing the temperature ofthe furnace from the second temperature to a third temperature higherthan the second temperature; and a fifth thermal process for maintainingthe temperature of the furnace at the third temperature.
 16. The methodof claim 15, wherein the first to fifth thermal processes aresuccessively performed in the same furnace, wherein a second thermalprocess time of the second thermal process is longer than a firstthermal process time of the first thermal process and a third thermalprocess time of the third thermal process, and wherein the third thermalprocess time is equal to or longer than the first thermal process time.17. The method of claim 15, wherein the first thermal process maintainsthe temperature of the furnace at the first temperature of 350° C. to450° C. for 5 minutes to 15 minutes, wherein the third thermal processmaintains the temperature of the furnace at the second temperature of500° C. to 600° C. for 10 minutes to 20 minutes, wherein the secondthermal process increases the temperature of the furnace from the firsttemperature to the second temperature for 15 minutes to 25 minutes,wherein the fifth thermal process maintains the temperature of thefurnace at the third temperature of 800° C. to 1000° C. for 15 minutesto 30 minutes, and wherein the fourth thermal process increases thetemperature of the furnace from the second temperature to the thirdtemperature for 5 minutes to 15 minutes.
 18. The method of claim 15,wherein the dehydrogenation process is performed through the first tothird thermal processes.
 19. The method of claim 15, wherein therecrystallization process is performed through the fourth thermalprocess.
 20. The method of claim 15, wherein the emitter regionactivating process and the front surface field region activating processare performed through the fifth thermal process.